Method of electrolytically coating and etching bearing surfaces



Dec. 2, 1952 I s. c. WILSDON I 2,620,296

METHOD OF ELECTROLYTICALLY COATING AND ETCHING BEARING SURFACES Filed July 14, 1947 l I I I I I I I 3' I I- I I I 3 I I I l I I I I I I l I I I I I I I f I I I I F I I III I I III I I: I I II. I I-4' A II I I I I *II I I I I I I II I II II I I I I I I I I I I I I I I l I I 1 I I I I I '1 I III I I I I-*- II I I ''I I I I I' I I I I l I I I 5 I I I 4 I I I I I I I I 3 I I I I I I I 3'I I I I I I I I I I l I I I I l G I I I I 6 I I L I I I Ingmar mQCQM;

Attorney.

Patented Dec. 2, 1952 METHOD OF ELECTROLYTICALLY COATING AND ETCHING BEARING SURFACES Sydney Charles Wilsdon, Olton, England, assignor to Monochrome Limited, Redditch, England, a

British company Application July 14, 1947, Serial No. 760,762 In Great Britain February 22, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires February 22, 1963 3 Claims.

This invention relates to chromium surface layers on cylinder bores, shafts and the like, and is more particularly concerned with the treatment and finishing of said surfaces after the metal has been electrolytically deposited thereon and the surface has been ground or honed.

It is well known that surfaces so treated are very hard and smooth thus greatly reducing the rate of wear when applied say to the cylinder bores or cylinder liners of engines, but owing to the smoothness of said surface, it does not hold or retain oil, and it is therefore diificult to ensure and maintain the required amount of lubricant over the surface of the cylinder bore or liner to avoid the objectionable results arising from insufiicient lubrication.

It has been previously proposed to provide a process wherein a layer of chromium is deposited electrolytically on the surface of a cylinder bore, and the chromium layer then treated for a short time with a reversedcurrent so that the bore becomes the anode, with the result that a certain amount of the chromium is removed from the surface and numeroussmall grooves, pits or depressions are formed in the surface, such being adapted to retain oil under working conditions. i

The object of the invention is to provide new or improved means for treatment of the aforesaid surfaces, whereby pits, depressions or grooves are formed in any desired or defined positions therein, which are adapted to retain oil and thus ensure eflicient lubrication between the moving parts, and at the same time leaving a considerable part of the surface unaffected and at its original hardness, to provide maximum resistance to wear.

According to this invention a layer of chromium is electrolytically deposited on thebore of a cylinder liner or the like which, if necessary, is subsequently ground or honed to the required finished size or dimension. A sleeve or casing of plastic or other suitable material is arranged to cover or surround the surface of the article to be treated, and the said article with the perforated sleeve attached thereto, which is arranged to constitute the anode, is immersed in an electrolytic bath containing a solution of caustic soda, chlorides, chromic acid, or any suitable chromium plating solution. Also immersed in the electrolytic bath is a cathode, comprising a bar of steel or other suitable material, which is so disposed in said bath that the electric current flows thereto from the article constituting the anode through the holes or slots in the aforesaid casing, and the chromium or like surface adjacent to the perforations in the casing is partly or completely removed, thus forming correspondingly disposed recesses or grooves which are adapted to form pockets for retaining oil under all working conditions.

One practical method of carrying the invention into effect will now be described with reference to the accompanying drawings, in which Figures 1 and 2 show respectively a front and a side elevation of a cylinder liner mounted in a frame or holder ready for immersion in an electrolytic bath containing a solution of caustic soda, chlorides, chromic acid, or any suitable chromium plating solution, for treatment in accordance with this invention.

Figure 3 shows a transverse sectional view taken on line A-A, Figure 1.

Figure 4 shows in sectional elevation part of a cylinder liner after treatment in accordance with this invention.

Figure 5 shows a side elevation of the perforated plastic sleeve adapted to be placed in the cylinder liner.

In one convenient arrangement for the treatment according to this invention of a cylinder liner that has been previously chromium plated and subsequently ground or honed to the required internal dimension or size, I provide a sleeve I, of plastic or other suitable material, in which are formed holes or perforations 2 of any desired shape and disposition. In the example shown in Figure 5 the said holes 2 are shown disposed in vertical and horizontal alignment, but if desired said holes may be disposed in any other formation, such as curved or spiral.

The aforesaid perforated sleeve I may be conveniently made from a sheet or strip of plastic material in which are formed the desired perforations, the said perforated sheet being rolled into a cylindrical form and its abutting edges fixed together by a plastic glue, or by other suitable means. i i

A perforated sleeve such as before described is fixed within a cylinder liner 3 that has been previously chromium plated and ground or honed to the required finished dimension. The external diameter of said perforated sleeve is preferably such that provides a frictional fit within the cylinder liner, thereby providing the means whereby it is held in position.

The cylinder liner 3 is mounted in a two part clamp 4 secured together by clamping bolts 5. On one part of the said clamp 4 are welded vertically disposed rods 6 to which are fixed top and bottom plates 7 and 8 and an intermediate plate 9. On the bottom plate 8 is mounted an insulating pad l provided on its upper side with a stem part I I, said pad being arranged to provide a support for a steel bar l2 which comprises the cathode, the upper end of said bar being supported in a rubber 01' like insulating bush [3 mounted in a central hole in the intermediate plate 9. To the aforesaid bar [2 constituting the cathode is attached a cable M.

To the top plate 1 is fixed a clip l which provides a support for the cylinder liner as the anode within an electrolytic bath, containing a solution of caustic soda, chlorides, chromic acid or the like.

The electric current flowing from the aforesaid anode constituted by the cylinder liner to the cathode passes through the holes in the perforated sleeve I, and partly or completely removes adjacent thereto the chromium or like plated surface on the said cylinder liner 3, as shown in Figure 4, thus forming correspondingly disposed recesses l6 which are adapted to form pockets for retaining oil under all working conditions.

The shape or configuration and disposition of the holes in the plastic sleeve 1 may be modified as desired, for example, instead of round holes they may comprise elongated slots, and said holes or slots may be disposed in curved or spiral formation.

For treatment of the plated surface of a shaft or the like, the perforated casing may conveniently comprise a sheet of perforated steel or plastic material, shaped and bent to surround the chromium plated surface of the article to be treated, in the manner previously described, whereby holes or pockets are formed in said surface.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A process of treating a machine part to provide an electrolytically-deposited bearing surface thereon, which comprises electrolytically depositing a metallic layer on such a part to a depth to provide a bearing surface of substantially a desired final bearing size, covering the electrolytically-deposited bearing surface by a mask having perforations distributed over its area and which is resistant to attack by an electrolytic etching solution, immersing in a bath of an electrolytic etching solution the part having the metallic layer electrolytically deposited thereon and the perforated mask covering such layer, and passing an electric current from an external source through the bath of electrolytic etching solution in such direction that said part constitutes the anode until the portions of the electrolytically-deposited metallic layer exposed through the perforations in the mask to the etching solution are etched to a depth sufficient to form shallow lubricant retaining recesses while the portions of said layer covered by the portions of the mask intervening the perforations therein are not exposed to the etching solution and remain unetched and smooth,

2. A process of treating machine parts which comprises immersing a machine part in an electrolytic bath, passing an electric current derived from an external source of supply through the electrolytic bath in such manner that the part constitutes the cathode until the part has been provided with an electro-deposited metallic bearing surface which is hard and wear-resisting and has thereby substantially attained its final plated size, removing said plated part from the electrolytic bath, covering the electro-deposited metallic bearing surface with a perforated mask which is resistant to attack by an electrolytic etching solution for said bearing surface, immersing the plated part so covered in an electrolytic etching solution for said bearing surface, passing an electric current derived from an external source of supply through said electrolytic etching solution in such manner that the portions of the electro-deposited metallic bearing surface exposed to the etching solution through the perforations in the mask constitute a plurality of spaced, interconnected anodes until shallow spaced recesses of sufiicient area and depth to retain lubricant are formed in the metallic bearing surf-ace by partial removal of those positions of said bearing surface exposed to said electrolytic etching solution through said perforations, the portions of said bearing surface covered by the mask and not exposed to said electrolytic etching solution remaining smooth and unetched, and thereafter removing the treated part from the electrolytic etching solution and the perforated mask from the treated part.

3. A process of treating machine parts which comprises immersing a machine part in an electrolytic bath, passing an electric current derived from an external source of supply through the electrolytic bath in such manner that the part constitutes the cathode until the part has been provided with an electro-deposited metallic bearing surface which is hard and wear-resisting and has thereby substantially attained its final plated size, removing said plated part from the electrolytic bath, covering the electro-deposited metallic bearing surface with a perforated mask which is resistant to attack by an electrolytic etching solution for said bearing surface, immersing the plated part so covered in electrolytic etching solution for said bearing surface, passing an electric current derived from an external source of supply through said electrolytic etching solution in such manner that the portions of the electro-deposited metallic bearing surface exposed to the etching solution through the perforations in the mask constitute a plurality of spaced inter-connected anodes until shallow, spaced, recessed areas are formed in the metallic bearing surface by partial removal of those portions of said bearing surface exposed to said electrolytic etching solution through said perforations, the portions of said bearing surface covered by the mask and not exposed to said electrolytic etching solution remaining smooth and unetched and having a surface area in excess of the total surface area of those portions of said bearing surface exposed to said electrolytic etching solution, and thereafter removing the treated part from the electrolytic etching solution and the perforated mask from the treated part.

SYDNEY CHARLES WILSDON.

(References on following page) 2,620,296 5 6 REFERENCES CITED FOREIGN PATENTS The following references are of record in the Number Country Date me i PATENTS 563,435 Germany Nov. 5, 1 932 Number Name BM 5 OTHER REFERENCES 422 677 Dam July 1181922 Amateur Craftsmans Cyclopedia," by Gros- Booe Set and Dunlap page 2,187,626 Merriman Jan. 16, 1940 2,314,604 Van der Hurst; Mar. 23, 1943 10 2,343,569 Neely et a1 Mar. 7, 1944 2,433,457 Jarrett et a1 Dec. 30, 1947 

1. A PROCESS OF TREATING A MACHINE PART TO PROVIDE AN ELECTROLYTICALLY-DEPOSITED BEARING SURFACE THEREON, WHICH COMPRISES ELECTROLYTICALLY DEPOSITING A METALLIC LAYER ON SUCH A PART TO A DEPTH TO PROVIDE A BEARING SURFACE OF SUBSTANTIALLY A DESIRED FINAL BEARING SIZE, COVERING THE ELECTROLYTICALLY-DEPOSITED BEARING SURFACE BY A MASK HAVING PERFORATIONS DISTRIBUTED OVER ITS AREA AND WHICH IS RESISTANT TO ATTACK BY AN ELECTROLYTIC ETCHING SOLUTION, IMMERSING IN A BATH OF AN ELECTROLYTIC ETCHING SOLUTION THE PART HAVING THE METALLIC LAYER ELECTROLYTICALLY DEPOSITED THEREON AND THE PERFORATED MASK COVERING SUCH LAYER, AND PASSING AN ELECTRIC CURRENT FROM AN EXTERNAL SOURCE THROUGH THE BATH OF ELECTROLYTIC ETCHING SOLUTION IN SUCH DIRECTION THAT SAID PART CONSTITUTES THE ANODE UNTIL THE PORTIONS OF THE ELECTROLYTICALLY-DEPOSITED METALLIC LAYER EXPOSED THROUGH THE PERFORATIONS IN THE MASK TO THE ETCHING SOLUTION ARE ETCHED TO A DEPTH SUFFICIENT TO FORM SHALLOW LUBRICANT RETAINING RECESSES WHILE THE PORTIONS OF SAID LAYER COVERED BY THE PORTIONS OF THE MASK INTERVENING THE PERFORATIONS THEREIN ARE NOT EXPOSED TO THE ETCHING SOLUTION AND REMAIN UNETCHED AND SMOOTH. 